This invention relates to combustion gas turbines and the fuel supply systems therefor.
Since the end of World War II, combustion gas turbines have been utilized in many industrial applications and have taken a prominent position as energy producers. For example, turbines are utilized in conjunction with oil refineries to burn waste and by-product gases from the refinery as fuel for the turbine to produce electricity which can be used or sold to an electric company and steam which is utilized by the oil refinery. A facility which produces steam for use by an oil refinery and electricity for use and sale is commonly referred to as a cogeneration plant.
A typical turbine used at a cogeneration plant and in other applications, takes in air which is compressed and forced into a combustion chamber inside the turbine. The gases produced at the oil refinery flow through fuel lines to nozzles in the combustion chambers where the fuel is combusted thereby heating the air and increasing the pressure in the combustion chamber. The products of combustion are allowed to expand inside stationary and rotating turbine blades in the turbine to impart torque to the turbine shaft which is connected to the rotating turbine blades. The rotation of the turbine shaft is utilized in many ways including, for example, to power a generator to produce electricity and to power an air compressor as a combustion air source.
In a typical turbine, there are ten flame nozzles spaced around the circumference of the turbine and each flame nozzle comprises an outer ring nozzle and an inner ring nozzle. The inner ring nozzle is supplied with butane and the outer ring nozzle is supplied with natural gas, refinery waste, or a mixture of the two. Each has a plurality of fuel holes through which the respective gas is passed. It is important that all the fuel holes remain open so that the shape of the flame emanating from the flame nozzle is uniform and the amount of fuel being burned and turbine power can be controlled. Though not unique to cogeneration plants, it is frequently the case that the fuel gas produced by the oil refinery is contaminated with debris such as scale and coke. Frequently, the debris is large enough to clog the holes in the natural gas nozzle. This restricts the flow of gas through the nozzle and deforms the flame shape creating temperature differences across the turbine which can lead to equipment damage and cause the turbine to perform inefficiently, shut down, or otherwise malfunction.
Extra maintenance above and beyond the manufacturer's recommended routine maintenance is required when the frequency with which the fuel holes become clogged with debris is increased. The extra maintenance, equipment damage, inefficient performance, shut downs, and other malfunctions all increase the cost of running the turbine. Further cost is added to the operation of the turbine by clogged flame nozzles because the nozzles must be sent off site to a qualified repair facility, usually the manufacturer, for cleaning and repair. It is desirable, therefore, to prevent debris from clogging the fuel holes.